Device for continuous fuel injection

ABSTRACT

A device for continuous injection of fuel into the intake line of a multi-cylinder mixture-compressing internal combustion engine is described, the said engine comprising an air pump (9) delivering a carrier air current branched off the intake line (2) and a fuel pump (4) which delivers the fuel from a fuel tank (3) to a metering device (7), apportioning the fuel to the carrier air current as a function of the operating state of the internal combustion engine. In order to ensure the best possible uniform and precise metering of the fuel of the fuel to the individual cylinders of the internal combustion engine, means for dividing the carrier air current among the carrier air injection lines (29) separately associated with the individual cylinders of the internal combustion engine are to be provided. Furthermore, the metering device is to be constituted by an injection valve (7) with injection lines (1) (36) each separately associated with the carrier air injection lines (29) and opening into the same (FIG. 1).

The invention concerns a device for continuous fuel injection into theintake line of a multi-cylinder, mixture-compressing internal combustionengine in accordance with the definition of the species in claim 1.

In case of such fuel injection devices, known, e.g., from German DE-OSNos. 29 20 636 and 32 22 000, the fuel is metered by means of aninjection nozzle controlled by a control means into a carrier aircurrent, branched off the intake line, before the mixture of fuel andsupporting air formed in this manner and subsequently distributed to theindividual cylinders of the internal combustion engine is injected intothe intake line of the internal combustion engine, namely, the intakemanifolds associated with the individual cylinders of the internalcombustion engine, a short distance ahead of the intake valves thereof.The advantage of such an injection device consists in that for injectionof the fuel-air mixture under pressure into the intake manifolds, noinjection nozzles such as utilized in customary fuel injection devicesare necessary inasmuch as the mixture under pressure, even if in smallquantities, expands on entering the intake manifolds and thereby isfinely divided and sprayed. This favorable [fuel] preparation effect isfurther enhanced by the partial fuel evaporation which occurs onexpansion of the fuel-air mixture.

In these known fuel injection devices, difficulties occur which are dueto the fact that the fuel-air mixture, formed by injection of the fuelinto the carrier air current through a center fuel injection nozzle,prior to delivery into the individual intake manifolds must be dividedamong the individual cylinders. Thereby a special problem occurs becausethe mixture to be divided is a two-phase mixture composed of a liquidfuel and gaseous air which, for the purpose of combustion with a highefficiency and low in exhaust gases, must be divided in the cylinders ofthe internal combustion engine as uniformly and as precisely aspossible, particularly in view of the liquid phase.

Therefore, the purpose of the invention is to provide of the kindindicated a fuel injection device fo the kind indicated whereby theproblems of a uniform allotment of the fuel to the individual cylindersof the internal combustion engine are solved in a simple, low-costmanner.

This purpose is attained by providing the fuel injection device withmeans for dividing the carrier air current among carrier air injectionlines separately associated with the individual cylinders of theinternal combustion engine and a metering device comprising an injectionvalve having injection openings each individually associated with andopening into the carrier air injection lines.

Further suitable refinements of the invention include injection lineswhich branch off at equal intervals along the circumference of an aircarrier reservoir, and are connected to a pressure side of an air pump.Furthermore, each of the injection openings is aligned toward adownstream end of the injection lines, the openings opening into zonesof the carrier injection lines whose cross-sections are restricted in anozzle-like fashion.

The drawing represents an example of an embodiment of the inventionwhich will be explained in detail in the following.

FIG. 1 is a schematic circuit diagram of a fuel injectin deviceaccording to the invention, and

FIG. 2, is a representation of the dosing device on an enlarged scale.

In the circuit diagram of the fuel injection device shown in FIG. 1, -1-designates a part of a customary mixture-compressing combustion engineand -2- an intake line system leading to the said combustion engine,which system is provided with an intake distributor -2a- and a number ofintake manifolds -2b-associated with the individual cylinders of thecombustion engine -1-.

-9- designates an air pump and -4- a fuel pump which may be driveneither separately or combined so as to form an assembly by use of acommon driving motor constituted, e.g., by an electric motor, associatedwith the two pumps.

The fuel pump -4- sucks in fuel from a fuel tank -3- and delivers saidfuel by way of a fuel line -24- in which is arranged a filter -5- to afuel metering device constituted by an injection valve -7- which, inaccordance with the signals of a control means -10-, delivers a fuelquantity associated with the operating condition of the combustionengine at the time. In a mixture-forming and dividing device -8- thefuel is injected into a carrier air current which by way of a line -21-is delivered by the air pump -9- which on the suction side is connectedwith the intake line system -2- of the combustion engine -1-. Thecarrier air current employed to deliver the fuel metered through theinjection valve -7- into the cylinders of the combustion engine thus isbranched off the air current sucked in by the combustion engine.

Fuel metering is obtained in each case separately into partial carrierair currents previously divided for the individual cylinders of thecombustion engine and subsequently transported by way of individualinjection lines -23- to the intake manifolds -2b- associated in eachcase with the cylinders of the combustion engine -1-. The mixturedelivered through the injection lines -23- is finally injectedcontinuously in the vicinity of the intake valves of the combustionengine and, with the intake valves open, is forwarded together with themain air current into the combustion chambers.

In FIG. 1 of the drawing, -22- designates a branch line branching offthe pressure-side delivery air line -21- the said branch line connectedwith a fuel pressure regulator -6- determining the pressure in the fuelline -24-. The fuel pressure regulator conducts the excess fuel via areturn line into the fuel tank -3-.

The control means designated by -10- controls the injection valve -7-effecting the fuel metering, among others as a function of the airquantity sucked in by the combustion engine -1-, towards which end isprovided in the intake line system -2- an air quantity meter designatedby -14-, and also as a function of the temperature and the speed of thecombustion engine, towards which end are present corresponding sensorsin the form of a temperature sensor -11- arranged on the cylinder block-1- of the internal combustion engine and an ignition distributordesignated by -13-.

A sensor determining the intake air temperature is provided as indicatedby -15-. It is likewise connected with the control means 10 for thepurpose of signal delivery as is a throttle valve switch -12- fordetecting the position of the throttle valve -17-.

Furthermore, -20- designates an auxiliary air valve arranged in theintake line system -2-, which valve serves the correction of the airquantity, delivered in particular during warming-up, and bypasses thethrottle valve designated by -17-, whereas -25- represents an idlingspeed adjustment screw and -26- an idling mixture adjustment screw.Finally, -18- designates an ignition-starting switch and -19- a batteryfor electric current supply which may be constituted, e.g., by thecustomary electric system battery of the vehicle, while -16- designatesa relay combination by means of which, on actuation of theignition-starting switch -18- the fuel pump -4- and the air pump -9- areconnected.

In FIG. 2 there is represented on an enlarged scale the mixture formingand dividing device -8-, with an injection valve -7- which, rather thaninjecting the fuel centrally into one carrier air line -23- common toall injection lines, injects the fuel into individual carrier airinjection lines -29-, each connected with an injection line -23-, and ineach case associated with a cylinder of the combustion engine.

From the example of an embodiment shown in FIG. 2, it furthermorebecomes apparent that the injection valve -7- is provided with a headpart -33- with a valve body -35- actuable, e.g. by electromagneticmeans, not shown here, and held in a valve housing -34-. In the headpart -33- of the injection valve -7- are incorporated here the carrierair injection lines -29- leading separately to the individual cylindersas well as injection openings -36- associated with the said carrier airinjection lines and opening into them, by way of which injectionopenings the fuel is delivered in quantities associated in each casewith the individual cylinders.

The injection openings -36- can open into the carrier air injectionlines -29- in points in which said lines are provided with nozzle-likeconstrictions 28. The delivery of the fuel at such constricted crosssections of the carrier air lines offers the advantage that, as a resultof the larger air flow velocity occurring at such a point, the pressurelevel required for injection of the fuel and to be provided by the fuelpump can be reduced (injector effect).

Furthermore, it is of advantage to align the injection openings -36- insuch a manner that they inject the fuel in the direction of the airflow, i.e., in the direction towards the downstream ends of the carrierair injection lines -29-. In this manner, a more rapid fuel transport isensured even at unfavorable operating conditions and it can be preventedthat the fuel flows back in opposition to the air flow direction intothe carrier air reservoir where it can cause a non-uniform fueldistribution in the individual cylinders.

In FIG. 2 of the drawing, -30- and -31- show separate housing componentsof the mixture forming and dividing device -8- which, with interpositionof sealing rings -32- and -37- are connected with each other and,respectively, the injection valve -7-.

In comparison with prior known fuel injection devices, the essentialadvantage of the present invention consists in that the fuel is notdelivered centrally into the carrier air and subsequently a distributionof the carrier air-fuel mixture to the individual cylinders is obtainedbut rather, the carrier air is initially divided among the individualcylinders and subsequently, the fuel, likewise apportioned separately tothe individual cylinders of the combustion engine, is delivered to thepartial carrier air currents through a single injection valve with anumber of injection openings corresponding to the number of cylinders.Inasmuch as the separate division of the individual phases, namely thegaseous phase of the carrier air and the liquid phase of the fuel, canbe obtained with substantially fewer problems than the division of atwo-phase flow required after mixing, the fuel metering in the lattercase is achieved with substantially more precision and uniformity. Ofcourse, it becomes necessary that the injection openings of theinjection valve can be rendered precisely so that from them aredelivered equal quantities of fuel in each case. On the other hand, thedivision of the carrier air among the individual phases is less criticalsince small differences in the quantities apportioned will not result inany serious effects on the operational behavior of the combustionengine.

We claim:
 1. Device for continuous injection of fuel into the intakelines of a multi-cylinder mixture-compressing internal combustionengine, with an air pump delivering a carrier air current branched offthe intake line and with a fuel pump which delivers the fuel from a fueltank to a metering device which apportions the fuel to the carrier aircurrent as a function of the operating state of the internal combustionengine, the device comprising means for division of the carrier aircurrent among carrier air injection lines separately associated with theindividual cylinders of the internal combustion engine, the meteringdevice being provided as an injection valve having a head part and avalve body which is adjustable relative to said head part so as todeliver the fuel through separate injection openings provided in saidinjection valve so as to be individually associated with and openinginto the carrier air injection lines said head part of the injectionvalve being provided with an annular carrier air reservoir whichsurrounds the injection valve concentrically and is connected to the airpump, said carrier air injection lines being provided so as toindividually branch off the carrier air reservoir at uniform intervalsover the circumference of said reservoir.
 2. Device for continuousinjection of fuel into an intake line of a multi-cylindermixture-compressing internal combustion engine, with an air pumpdelivering a carrier air current branched off said intake line and witha fuel pump which delivers the fuel from a fuel tank to a meteringdevice apportioning the fuel to the carrier air current as a function ofthe operating state of the internal combustion engine, characterized inthat means are provided for division of the carrier air current amongcarrier air injection lines separately associated with the individualcylinders of the internal combustion engine and in that the meteringdevice comprises an injection valve having injection openings eachindividually associated with the carrier air injection lines and openinginto zones of the carrier air injection lines whose cross sections areconstricted in a nozzle-like fashion.
 3. Injection device as defined inclaim 1, wherein each of the injection openings (36) of the injectionvalve (7) are aligned towards a downstream-end of each of the carrierair injection lines.
 4. Injection device as defined in claim 1, whereinthe carrier air injection lines are provided with zones havingcross-sections constricted in a nozzle-like manner, each of theinjection openings of the injection valve being provided so as to openinto one of the zones of contricted cross-section.
 5. The device ofclaim 2, wherein a carrier air reservoir connected to a pressure side ofthe air pump is provided from which reservoir branch off a number of airinjection lines corresponding to the number of cylinders of the internalcombustion engine.
 6. The device of claim 5, wherein said carrier airinjection lines branch off regularly over the circumference of thecarrier air reservoir.